Attempts will be made to regulate the expression of the c-src and other cellular proto-oncogenes. The approach will involve construction of plasmids that encode proto-oncogene antisense RNAs that can act to arrest the translation of the homologous mRNA in vivo. Such plasmids will be transfected into polyoma transformed rat and mouse fibroblasts, as well as normal primary and established cells, and teratocarcinoma cells. A long term objective includes the insertion of these plasmids into mouse embryos and establishment of transgenic mice.